Low-threshold continuous-wave 1.5-/spl mu/m GaInNAsSb lasers grown on GaAs

We present the first continuous-wave (CW) edge-emitting lasers at 1.5 /spl mu/m grown on GaAs by molecular beam epitaxy (MBE). These single quantum well (QW) devices show dramatic improvement in all areas of device performance as compared to previous reports. CW output powers as high as 140 mW (both facets) were obtained from 20 /spl mu/m /spl times/ 2450 /spl mu/m ridge-waveguide lasers possessing a threshold current density of 1.06 kA/cm/sup 2/, external quantum efficiency of 31%, and characteristic temperature T/sub 0/ of 139 K from 10/spl deg/C-60/spl deg/C. The lasing wavelength shifted 0.58 nm/K, resulting in CW laser action at 1.52 /spl mu/m at 70/spl deg/C. This is the first report of CW GaAs-based laser operation beyond 1.5 /spl mu/m. Evidence of Auger recombination and intervalence band absorption was found over the range of operation and prevented CW operation above 70/spl deg/C. Maximum CW output power was limited by insufficient thermal heatsinking; however, devices with a highly reflective (HR) coating applied to one facet produced 707 mW of pulsed output power limited by the laser driver. Similar CW output powers are expected with more sophisticated packaging and further optimization of the gain region. It is expected that such lasers will find application in next-generation optical networks as pump lasers for Raman amplifiers or doped fiber amplifiers, and could displace InP-based lasers for applications from 1.2 to 1.6 /spl mu/m.     

Improved CW operation of GaAs-based QC lasers: T/sub max/= 150 K

We present a substantial improvement in the CW performance of GaAs-based quantum cascade lasers with operation up to 150 K. This has been achieved through suitable changes in device processing of a well-characterized laser. The technology optimizes the current injection in the laser by reducing the size of the active stripe whilst maintaining a strong coupling of the optical mode to preserve low current densities. The reduction of total dissipated power is critical for these lasers to operate CW. At 77 K, the maximum CW optical power is 80 mW, threshold current is 470 mA, slope efficiency is 141 mW/A, and lasing wavelength /spl lambda//spl sim/10.3 /spl mu/m.     

Room-temperature continuous-wave operation of GaInNAsSb laser diodes at 1.55 /spl mu/m

The first 1.55 /spl mu/m room-temperature continuous-wave (CW) operation of GaAs-based laser diodes utilising GaInNAsSb/GaNAs double quantum well active regions grown by molecular beam epitaxy is reported. In electrically-pumped CW operation the narrow ridge waveguide devices have a room temperature lasing wavelength of 1550 nm near threshold, increasing to 1553 nm at thermal rollover. The CW threshold current was 132 mA for a 3/spl times/589 /spl mu/m device, with a characteristic temperature of 83 K, measured in pulsed mode between 20 and 70/spl deg/C.     

Low-threshold high-T/sub 0/ 1.3-/spl mu/m InAs quantum-dot lasers due to p-type modulation doping of the active region

P-type doping is used to demonstrate high-To, low-threshold 1-3 /spl mu/m InAs quantum-dot lasers. A 5-/spl mu/m-wide oxide confined stripe laser with a 700-/spl mu/m-long cavity exhibits a pulsed T/sub 0/ = 213 K (196 K CW) from 0/spl deg/C to 80/spl deg/C. At room temperature, the devices have a CW threshold current of /spl sim/4.4 mA with an output power over 15 mW. The threshold at 100/spl deg/C is 8.4 mA with an output power over 8 mW.     

Continuous-wave operation of quantum cascade laser emitting near 5.6 /spl mu/m

Buried heterostructure quantum cascade lasers emitting at 5.64 /spl mu/m are presented. Continuous-wave (CW) operation has been achieved at -30/spl deg/C for junction down mounted devices with both facets coated. A 750 /spl mu/m-long laser exhibited 3 mW of CW power with a threshold current density of 5.4 kA/cm/sup 2/.     

Highly reliable 60/spl deg/C 50-mW operation of 650-nm band window-mirror laser diodes

High-power GaInP QW laser diodes with a window-mirror-structure lasing at a wavelength of around 650 nm have been fabricated. The maximum light output power over 150 mW has been realized without optical mirror damage. In addition, the laser shows the fundamental-mode-operation at 50 mW and the dynamic characteristics sufficient for recordable digital versatile disc (DVD) applications. The lasers have been operating for 2000 h under the condition of CW, 50 mW, and 60/spl deg/C, for the first time.     

Damping-limited modulation bandwidths up to 40 GHz in undoped short-cavity In/sub 0.35/Ga/sub 0.65/As-GaAs multiple-quantum-well lasers

We demonstrate record direct modulation bandwidths from MBE-grown In/sub 0.35/Ga/sub 0.65/As-GaAs multiple-quantum-well lasers with undoped active regions and with the upper and lower cladding layers grown at different growth temperatures. Short-cavity ridge waveguide lasers achieve CW direct modulation bandwidths up to 40 GHz for 6/spl times/130 /spl mu/m/sup 2/ devices at a bias current of 155 mA, which is the damping limit for this structure. We further demonstrate large-signal digital modulation up to 20 Gb/s (limited by the measurement setup) and linewidth enhancement factors of 1.4 at the lasing wavelength at threshold of /spl sim/1.1 /spl mu/m for these devices.     

Continuous-wave operation of all-epitaxial InP-based 1.3 /spl mu/m VCSELs with 57% differential quantum efficiency

All-epitaxial InP-based 1.3 /spl mu/m VCSELs with a record-high continuous-wave differential quantum efficiency (57%) for single active region long-wavelength devices are demonstrated. Low-loss optical mode confinement is achieved through a selectively etched undercut tunnel-junction aperture. Singlemode continuous-wave lasing was observed up to 87/spl deg/C and the room-temperature output power was 1.1 mW at a current of 4.1 mA and a wavelength of 1.305 /spl mu/m.     

Short wavelength (/spl lambda//spl sim/4.3 /spl mu/m) high-performance continuous-wave quantum-cascade lasers

We report continuous-wave (CW) operation of a 4.3-/spl mu/m quantum-cascade laser from 80 K to 313 K. For a high-reflectivity-coated 11-/spl mu/m-wide and 4-mm-long laser, CW output powers of 1.34 W at 80 K and 26 mW at 313 K are achieved. At 298 K, the CW threshold current density of 1.5 kA/cm/sup 2/ is observed with a CW output power of 166 mW and maximum wall-plug efficiency of 1.47%. The CW emission wavelength varies from 4.15 /spl mu/m at 80 K to 4.34 /spl mu/m at 298 K, corresponding to a temperature-tuning rate of 0.87 nm/K. The beam full-width at half-maximum values for the parallel and the perpendicular far-field patterns are 26/spl deg/ and 49/spl deg/ in CW mode, respectively.     

2.0-/spl mu/m single-mode operation of InGaAs-InGaAsP distributed-feedback buried-heterostructure quantum-well lasers

Distributed-feedback (DFB) buried-heterostructure (BH) lasers with quantum-well active region emitting at 2.0 /spl mu/m have been fabricated and characterized. The lasers with four wells showed performance of practical use: threshold current as low as 15 mA for 600-/spl mu/m-long devices and CW single-mode output up to 5 mW at 2.03 /spl mu/m under operation current of 100 mA were observed. The current- and temperature-tuning rates of DFB mode wavelength are 0.004 nm/mA and 0.125 nm/K, respectively.     

High-power continuous-wave operation of quantum-cascade lasers up to 60/spl deg/C

High-temperature high-power continuous-wave (CW) operation of high-reflectivity-coated 12-/spl mu/m-wide quantum-cascade lasers emitting at /spl lambda/ = 6 /spl mu/m with a thick electroplated Au top contact layer is reported for different cavity lengths. For a 3-mm-long laser, the CW optical output powers of 381 mW at 293 K and 22 mW at maximum operating temperature of 333 K (60/spl deg/C) are achieved with threshold current densities of 1.93 and 3.09 kA/cm/sup 2/, respectively. At 298 K, the same cavity gives a maximum wall plug efficiency of 3.17% at 1.07 A. An even higher CW optical output power of 424 mW at 293 K is obtained for a 4-mm-long laser and the device also operates up to 332 K with an output power of 14 mW. Thermal resistance is also analyzed at threshold as a function of cavity length.     

650-nm vertical-cavity surface-emitting lasers: laser properties and reliability investigations

650-nm AlGaInP-AlGaAs-based oxide-confined VCSELs are investigated in dependence on the current aperture size. VCSELs with small aperture (a=5 /spl mu/m) have a maximum continuous-wave (CW) output power of about 1 mW at room temperature. They reach higher operating temperatures (T/sub max/=55/spl deg/C), have narrower beam profiles, less transverse modes, and a higher side mode suppression compared to large aperture VCSELs (a>13 /spl mu/m). The latter devices emit a CW-output power P=3 mW at 20/spl deg/C. Reliability tests of 655-nm devices show at 20/spl deg/C an output power of P/spl ap/0.4 mW over more than 1000 h and at 40/spl deg/C P/spl ap/0.1 mW over 500 h.     

High-power ridge waveguide InGaAsN lasers fabricated with pulsed anodic oxidation

High-power InGaAsN triple-quantum-well strain-compensated lasers grown by metal-organic chemical vapor deposition were fabricated with pulsed anodic oxidation. A maximum light power output of 145 mW was obtained from a 4-/spl mu/m ridge waveguide uncoated laser diode in continuous-wave (CW) mode at room temperature. The devices operated in CW mode up to 130/spl deg/C with a characteristic temperature of 138 K in range of 20/spl deg/C-90/spl deg/C.     

All-epitaxial InAlGaAs-InP VCSELs in the 1.3-1.6-/spl mu/m wavelength range for CWDM band applications

All-epitaxial InAlGaAs-InP vertical-cavity surface-emitting lasers grown by metal-organic chemical vapor deposition were successfully demonstrated in the wavelength ranging from 1.3 to 1.6 /spl mu/m. The devices showed the high performances such as single-mode output power of higher than 1.1mW, sidemode suppression ratio of 37 dB, divergence angle of 9/spl deg/, and CW operation of temperature up to 80 /spl deg/C. We achieved the modulation bandwidth exceeding 2.5 Gb/s and power penalty free transmission over 30 km.     

Electrically pumped room temperature CW VCSELs with 2.3 /spl mu/m emission wavelength

Continuous wave (CW) operation at room temperature of electrically pumped InGaAlAs/InP vertical-cavity surface-emitting lasers (VCSELs) at emission wavelengths as high as 2.3 /spl mu/m is demonstrated for the first time. Devices with 15 /spl mu/m active region diameter show a maximum output power of 0.75 mW at 20/spl deg/C and a maximum CW operating temperature of 45/spl deg/C.     

CW room-temperature operation of Y-junction semiconductor ring lasers

CW room-temperature lasing in Y-junction semiconductor ring lasers with radii as small as 50 mu m is reported. The dependence of the threshold current density on device dimensions is examined for radii in the range 50-200 mu m and for waveguide widths of 2-8 mu m. From these quantum-well devices, approximately 1 mW of CW single-frequency Te-polarised lasing output is obtained.<>     

Tunable twin-guide distributed feedback laser diodes with over 9 nm continuous electro-optic tuning range

Tunable twin-guide laser diodes at 1.55 /spl mu/m with a record electro-optic tuning range are presented. Employing an optimised device design, continuous tuning ranges of 9.3 and 11.0 nm are achieved in continuous-wave (CW) and pulsed operation, respectively. In CW operation, the output power of 300 /spl mu/m-long devices remains above 1 mW throughout the whole tuning range.     

High-power highly reliable 1.02-1.06-/spl mu/m InGaAs strained-quantum-well laser diodes

By growing the InGaAs active layer at temperatures lower than in conventional growth, we extended the lasing wavelength and presented the high reliability in InGaAs strained-quantum-well laser diodes. Equivalent I-L characteristics were obtained for 1.02-, 1.05-, and 1.06-/spl mu/m laser diodes with a cavity length of 1200 /spl mu/m. Maximum output power as high as 800 mW and fundamental transverse mode operation at up to 400 mW were obtained at 1.06 /spl mu/m and an 1800-/spl mu/m cavity. Stable operation was observed for over 14 000 h under auto-power-control of 225 mW at 50/spl deg/C for the 1.02-, 1.05-, and 1.06-/spl mu/m lasers with a 900-/spl mu/m cavity.     

Lasing characteristics of GaInAsP-InP strained quantum-well microdisk injection lasers with diameter of 2-10 /spl mu/m

We have obtained pulsed lasing operation in 2-5-/spl mu/m diameter microdisk injection lasers using GaInAsP-InP compressively-strained multiple-quantum-well (MQW) wafers around room temperature. The effective cavity volume of the 2-/spl mu/m-diameter device is the smallest among those for any type of electrically-pumped lasers. The threshold current of this device was as low as 0.2 mA. Cavity modes in emission spectra observed under CW conditions coincide well with theoretically predicted whispering gallery modes. Further reduction of diameter to less than 1.5 /spl mu/m will realize the condition for spontaneous emission almost coupling into a single mode, which results in thresholdless lasing operation.     

Monolithic, multiple-wavelength vertical-cavity surface-emitting laser arrays by surface-controlled MOCVD growth rate enhancement and reduction

Monolithic, multiple-wavelength vertical-cavity surface-emitting laser (VCSEL) arrays have been obtained by the surface-controlled enhancement and reduction of the MOCVD epitaxial growth rate, achieving a periodic, graded wavelength span greater than 30 nm. Room-temperature (RT), electrically pumped continuous-wave (CW) lasing is demonstrated, with uniform threshold currents of 5.5/spl plusmn/0.5 mA with typical output powers of 0.5 mW. We show here for the first time both the enhancement and the reduction of the growth rate of the entire VCSEL structure and demonstrate the controlled variation of the VCSEL lasing wavelength over a widened spectral range by exploiting both effects.